Gps And Xm Mounted Nearby

[+hummingbird1950]

I have an unusual problem (I think). I have an XM radio unit (Roady) in a swivel mount on the center of the dash of my truck. It uses an FM modulator built into the cig lighter adaptor, which is a good 18 inches away. When I put my GPSr cradle next to it, the unit will not acquire any satellites. If I move the GPSr to the left side, near the pillar, it immediately locks in and works just fine. The antenna for the XM is on the roof at the rear of the cab. The XM and the GPSr use adjacent power outlets.

 

I'd really like to have the GPSr in the center, rather than the left side.

 

Any thoughts?

[+Pelamore]

I'm no PhD, but I think you are in trouble.

The XM is broacasting a radio signal, the GPS satelites are broadcasting radio signals. Your GPSr is confused.

Many devices that transmit to your radio (Like XM Receivers) have the option to change the frequency they use. Look into that, it may be as simple as changing that frequency with a switch on the device. Even if you aren't using that feature, it may still be broadcasting if it does.

All radio transmitters suffer what I call "Signal Drift". It is supposed to broadcast on 99.1 for example, but also floods other frequencies just above and below. The general rule is smaller broadcaster more drift, closer more drift. You are getting both, hehe. You can try placing a piece of Aluminum foil between them to deflect some of the drifted signals. If your GPSr supports it, consider an external antenna for it, to increase the distance and reduce the drift it receives.

[+scott9282]

If I may, I have the same type of setup in my Grand Cherokee. An XM Roady on a bracket that is mounted behind the radio fascia plate, and a suction cup mount for a magellan sportrak map on the dash about 8" from the Roady.

 

What I did was have the Roady installed by BestBuy. The FM modulator is hidden out of sight, and the antenna for the XM unit is at the back of the Jeep by the liftgate. I have no problems with satellite reception, aside from the now normal sportrak EPE problems. But that happens when the GPSr is used outside of the Jeep, so XM isn't the problem.

 

You might want to see if the antenna wire for the XM is too close to the GPSr. My antenna wire is very thin, and probably not shielded. Since the XM signal is nowhere near normal radio channels (that is my understanding, and one of the reasons you need a modulator or special radio in dash) it may be close to the GPS satellite signal. With no shielding, you might be getting some low level interference. Try hiding the cable, that might be worth a shot.

[+Wacka]

Could it be that your windshield is tinted?. Some have a metallic coating and and don't allow sat lock. Maybe by putting it near the pillar, you are getting sats through the side window?

[+Renegade Knight]

All electronics generate a certain amount of EMF. Through design and sheilding they limit how much escapes to interfere with other electronics. Your XM Radio (or the FM Transmitter) apparently generates exactly the right type of EMF to interfere with your GPS.

 

What it means is that you will always have this problem as long as you have the same equipment. That's my best guess. If it works in the center of your rig when you don't have the XM Radio and FM transmitter in your rig, then that's the issue.

 

Wacka has also suggested another thing that can cause the problem in certain GM vehicles.

[+hummingbird1950]

Thanks, folks. I'll try a few things and see what happens, though having it on the left side all this weekend wasn't so bad after all, so I may just mount it there and be done with it.

[mloser]

I have a Pontiac Montana and my GPSr won't work in it well. I have to turn it sideways and practically stick it out the side window to use it. The radio antenna in my van is built into the windshield and basically is some sort of metallic plating on the glass to accomplish it.

 

I learned of this when I got EZ-PASS for the PA Turnpike. The EZ-PASS antenna normally goes on the inside of the windshield near the mirror, but there is a list of vehicles that need external antennas on the site at EZ-PASS external antenna list. If your vehicle is on it I bet that your windshield may be part of the problem.

 

I have an XM radio too, but it is never near my GPSr (in my other, non-shielded windshield)